Kinetics of diacylglycerol accumulation in response to vasopressin stimulation in hepatocytes of continuously endotoxaemic rats

Turco, Elena; Spitzer, Judy A.

doi:10.1042/bj2530073

Cited by 21 publications

(5 citation statements)

References 47 publications

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“…2-3 nmol of fatty acid/mg dry wt. of hepatocytes [38][39][40]. This rise occurs despite the presence of an important DAG kinase activity, which is also stimulated by VP, that may remove part of the DAG formed [41].…”

Section: Discussionmentioning

confidence: 99%

Lack of translocation of protein kinase C from the cytosol to the membranes in vasopressin-stimulated hepatocytes

Díaz-Guerra

1990

Biochemical Journal

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The ability of Ca2(+)-mobilizing hormones to promote changes in the subcellular distribution of protein kinase C (PKC) was studied in isolated hepatocytes. In recently isolated cells the distribution of PKC between the soluble and particulate fractions was 47 and 53% respectively. Exposure of the hepatocytes to 100 nM-vasopressin produced an increased phosphoinositide turnover, as reflected by the changes in the concentrations of inositol trisphosphate and Ca2+, and in glycogen phosphorylase a activity. However, the distribution of both PKC activity and [3H]phorbol dibutyrate binding between the cytosol and the membranes remained unchanged under these conditions. To determine the threshold values of the concentrations of Ca2+ and diacylglycerol required to produce a redistribution of PKC, the hepatocytes were treated with the Ca2+ ionophore ionomycin, and with permeant diacylglycerol derivatives. Hepatocytes incubated in the presence of 100 nM-vasopressin required concentrations of Ca2+ 2.5 times those produced physiologically by the hormone to produce translocation of PKC from the cytosol to the membranes. These studies suggest that, at least in hepatocytes, activation of PKC in response to Ca2(+)-mobilizing hormones involves only the pre-existent membrane-bound enzyme without affecting the soluble enzyme.

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Section: Discussionmentioning

confidence: 99%

Lack of translocation of protein kinase C from the cytosol to the membranes in vasopressin-stimulated hepatocytes

Díaz-Guerra

1990

Biochemical Journal

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“…Work by others has shown that in various cell types the DAG generated after stimulation may originate from several sources (Pelech & Vance, 1989;Exton, 1990). For example, cell stimulation may result in parallel activation of both a PIC and a phosphatidylcholinespecific phospholipase C, the latter producing a greater and prolonged accumulation of DAGs with a composition different from the PPI-derived DAG (Rodriguez de Turco & Spitzer, 1988;Pessin & Raben, 1989). In addition, the PPIderived DAG may exert a positive feedback effect by stimulating PLC to generate additional DAG from several phosphoglycerides (Exton, 1990).…”

Section: Discussionmentioning

confidence: 99%

The role of diacylglycerol in the exocytosis of the sperm acrosome. Studies using diacylglycerol lipase and diacylglycerol kinase inhibitors and exogenous diacylglycerols

Roldán

Harrison

1992

Biochemical Journal

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When ram spermatozoa were treated with Ca2+ and the ionophore A23187 to induce acrosomal exocytosis, a rise in diacylglycerol (DAG) mass was observed, concomitant with a rapid breakdown of [32P]P1-labelled phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-phosphate and a rise in [32P]Pi-labelled phosphatidate. Inclusion of the DAG lipase inhibitor RHC 80267 resulted in further but biphasic increases in DAG; there was an increasing accumulation of DAG with concentrations of RHC 80267 up to 10 microM, whereas higher concentrations produced lessening accumulation. Inclusion of RHC 80267 in the ionophore induction system also resulted in significant accelerations of the onset of exocytosis. In spermatozoa stimulated with Ca2+/A23187 and the DAG kinase inhibitor R59022, a similar increase in DAG levels together with stimulation of acrosomal exocytosis were observed. Preincubation of spermatozoa with sn-1-oleoyl-2-acetylglycerol, rac-1-oleoyl-2-acetylglycerol, sn-1,2-dioctanoylglycerol and sn-1,3-dioctanoylglycerol before treatment with Ca2+/A23187 resulted in a dose-dependent stimulation of exocytosis by all these isomers. Neomycin inhibited Ca2+/A23187-induced generation of DAG together with polyphosphoinositide breakdown, as well as acrosomal exocytosis. Inclusion of exogenous DAG, however, overcame the inhibitory effect of neomycin on exocytosis. Our results suggest that DAG has a key role in acrosomal exocytosis and that it acts as a messenger rather than as a substrate from which other active metabolites are generated. The lack of stereospecificity shown by the exogenous DAGs implies that DAG does not act by stimulating protein kinase C, but the metabolite's actual target in the sperm cell is as yet unclear.

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“…Selection of 3-and 30-h time points for analysis enabled us to compare 02 generation by liver NPC during the early response to LPS with that during a later phase, when morbidity is maximal and metabolic responses are at their nadir (25,53,55,70).…”

Section: Discussionmentioning

confidence: 99%

“…At 3 h, rats do not show signs of morbidity, yet at the hepatic cellular level the vasopressin-stimulated inositol lipid-mediated signal transduction is already impaired (54). At the 30-h time point, maximal morbidity and severe impairment of hepatocyte and adipocyte responses are observed (14,53,55,71).…”

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confidence: 99%

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Continuous infusion of Escherichia coli endotoxin in vivo primes in vitro superoxide anion release in rat polymorphonuclear leukocytes and Kupffer cells in a time-dependent manner

Mayer

Spitzer

1991

Infect Immun

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Continuous infusion of a nonlethal dose of Escherichia coli lipopolysaccharide (LPS) (0.5 mg/kg) in#dced early (3 h) accumulation of polymorphonuclear leukocytes (PMNL) in rat liver followed by later (30 h) greater extravasation of mononuclear phagocytes (MNP) (E. B. Rodriguez de Turco and J. A. Spitzer, J. Leukocyte Biol. 48:488-494, 1990). Nonparenchymal liver cells from rats treated for 3 and 30 h with LPS were recovered by centrifugal elutriation, yielding a 23-ml/min fraction (endothelial cells) and a 45-ml/min fraction (PMNL, Kupffer cells, and MNP), and compared for their capacity for basal and agonist-stimulated superoxide (02 ) production. Stimulation with phorbol myristate acetate and opsonized zymosan caused a dose-dependent release Of 02 from the 45-ml/min fraction derived from rats treated for 3 h with saline, but not from the 23-ml/min fraction. Further purification of the 45-ml/min fraction by discontinuous density gradient centrifugation into a Kupifer and a PMNL fraction revealed that most of the agonist-induced 02 release was generated by infiltrating PMNL at this early time point of LPS infusion. By 30 h of LPS infusion, although enhancement of the phorbol-12-myristate-13-acetateand opsonized zymosan-stimulated release of 02 was observed in the 45-ml/min fraction, but not in the 23-ml/min fraction, the maximum release of 02was smaller than that observed in the rats treated for 3 h. Our results support the following conclusions: (i) after a 3-h LPS infusion, PMNL found in the liver in increased numbers are also highly primed for agonist-stimulated release of 02while Kupifer cell priming is of a lesser extent; (ii) after a 30-h infusion of LPS, infiltrating MNP found in the liver in increased numbers are primed for agonist-induced 02 release, while priming of PMNL has diminished; (iii) at both 3 and 30 h of LPS infusion, liver endothelial cells are not significantly primed for agonist-stimulated 02 release; and (iv) in vivo priming by LPS infusion at both 3 and 30 h was not reversed by the experimental method used for cell recovery (ca. 3 h), thus suggesting that in vivo LPS priming of 02 release may ultimately lead to severe impairment of liver function and metabolism observed during endotoxemia and sepsis if not therapeutically blocked at an early time point.

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Kinetics of diacylglycerol accumulation in response to vasopressin stimulation in hepatocytes of continuously endotoxaemic rats

Cited by 21 publications

References 47 publications

Lack of translocation of protein kinase C from the cytosol to the membranes in vasopressin-stimulated hepatocytes

Lack of translocation of protein kinase C from the cytosol to the membranes in vasopressin-stimulated hepatocytes

The role of diacylglycerol in the exocytosis of the sperm acrosome. Studies using diacylglycerol lipase and diacylglycerol kinase inhibitors and exogenous diacylglycerols

Continuous infusion of Escherichia coli endotoxin in vivo primes in vitro superoxide anion release in rat polymorphonuclear leukocytes and Kupffer cells in a time-dependent manner

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